RAID (redundant arrays of inexpensive disks) apparatuses adopting a distributed cache memory-type storage system have conventionally adopted a redundant configuration including multiple control modules for controlling input of data to a storage and output of data therefrom, in order to improve performance and reliability. A process of reading data from a logical volume or a process of writing data thereinto is performed with respect to each control module.
Also, in order to improve reliability and the like, such a RAID apparatus has a remote copy function, called as “advanced copy”, that ensures the order. FIG. 33 is a drawing showing a related-art example of a RAID apparatus having a remote copy function that ensures the order. FIG. 33 shows a storage system that includes a RAID apparatus 3301 including control modules 00 and 01 and a RAID apparatus 3302 including control modules 10 and 11.
Each RAID apparatus includes: a recording buffer including a buffer for temporarily storing data stored in a storage medium or to be stored therein in areas obtained by dividing the buffer into multiple parts and a BIT (buffer index table) for storing indexes assigned to data stored in the buffer for each area; a buffer set storage section for storing buffer sets formed by combinations of one or two or more buffers included in a copy source apparatus where data to be copied is stored and one or two or more buffers included in a copy destination apparatus where data transmitted from the copy source apparatus is stored; and a storage medium for storing data.
When performing a remote copy that ensures the order, the copy source apparatus reads data to be copied from the storage medium and stores the read data in the recording buffer sequentially. When all areas of the recording buffer is exhausted or when a given time has elapsed, the copy source apparatus collectively transmits (hereafter, this transmission method will be referred to as “collective transmission method”) the data of the recording buffer to the copy destination apparatus 3302 connected to the copy source apparatus via a network on the basis of the buffer sets. At this time, the copy source apparatus also transmits the buffer sets.
On the other hand, when the copy destination apparatus 3302 receives the data from the copy source apparatus 3301, it temporarily stores the data in the recording buffer. Also, the copy destination apparatus 3302 stores the received buffer sets in its own buffer set storage section. When receiving all data, the copy destination apparatus 3302 loads the data of the recording buffer into a predetermined recording medium.
As seen above, the copy source apparatus 3301 transmits data by means of collective transmission method using the recording buffer so as to control the buffer sets collectively, while the copy destination apparatus 3302 loads the data on a buffer set-by-buffer set basis. Thus, the order is ensured.
FIG. 33 shows an example of a case where the number of control modules in the copy source apparatus 3301 is equal to that in the copy destination apparatus 3302 and the number of recording buffers included in the control modules in the copy source apparatus 3301 is equal to that in the copy destination apparatus 3302.
Similarly, if the number of control modules in the copy destination apparatus 3302 is larger than that in the copy source apparatus 3301 and the number of recording buffers included in the control modules in the copy destination apparatus 3302 is larger than that in the copy source apparatus 3301, it is possible to effectively use all the buffer sets of the copy source apparatus 3301.
However, there has been a problem that if the number of control modules in the copy source apparatus 3301 is larger than that in the copy destination apparatus 3302 and the number of recording buffers included in the control modules in the copy source apparatus 3301 is larger than that in the copy destination apparatus 3302, it is not possible to effectively use all the buffer sets of the copy source apparatus 3301.
FIG. 34 is a drawing showing an example of a case where the number of control modules in a copy source apparatus is larger than that in a copy destination apparatus. FIG. 34 shows a storage system including a RAID apparatus 3301 including control modules 00, 01, 02, and 03 and a RAID apparatus 3302 including control modules 10, and 11.
As in FIG. 33, each RAID apparatus includes: a recording buffer including a buffer for temporarily storing data stored in a storage medium or to be stored therein in areas obtained by dividing the buffer into multiple parts and a BIT for storing indexes assigned to data stored in the buffer for each area; a buffer set storage section for storing buffer sets formed by IDs of buffers of the copy source apparatus and IDs of buffers of the copy destination apparatus; and a storage medium for storing data.
For example, assume that the number of areas of a buffer of a control module is eight. The copy source apparatus 3301 includes four control modules, while the copy destination apparatus 3302 includes only two control modules. Therefore, if data is transmitted using the above-mentioned collective transmission method, the number of areas that can be used effectively among the areas of a buffer of a control module of the copy source apparatus 3301 is four, which is half, so the remaining buffer is not available.
In relation to the above-mentioned technology, there is known a back-up apparatus that is included in a disk array system and that monitors the use situation of a write buffer for temporarily storing write data, writes information stored in the buffer into a separately prepared, high-speed disk system when free space of the buffer is reduced, and writes back the sheltered data into the buffer when the use situation is improved. The related art is disclosed in Japanese Laid-open Patent Publication No. 2006-268420.
Also, there is known a virtually-ordered write method of, by achieving a low wait time with respect to a write performed by each host regardless of the distance between a primary apparatus and a secondary apparatus, providing consistency (recoverability) of the secondary apparatus at the time of a failure. The related art is disclosed in Japanese Laid-open Patent Publication No. 2006-523890.
Also, there is known a data copy method change method of, in a system including a control calculator, a host calculator, and first and second storage apparatuses, monitoring such as a variation in amount of access to the first storage apparatus by the host calculator when maintaining replica data of the first storage apparatus in the second storage apparatus by performing a remote data copy, and instructing the storage apparatuses to change the remote data copy method in accordance with the variation by using the control calculator. The related art is disclosed in Japanese Laid-open Patent Publication No. 2006-236019.
Also, there is known a storage system having a remote copy function that ensures the order assurance while maintaining superiority of scalability of a distributed cache memory-type storage system. The related art is disclosed in Japanese Laid-open Patent Publication No. 2006-260292.
Also, there is known a storage apparatus that prevents interruption of an application process by securing a reserved buffer for remote copy in advance and avoiding a buffer shortage in a communication performed using the buffer reservation subject. The related art is disclosed in Japanese Laid-open Patent Publication No. 2005-122235.
Also, there is known an inter-disk array apparatus remote data copy method of reducing overhead of the transmission protocol of update data and realizing a data update order ensuring function and a copy stop function. The related art is disclosed in Japanese Laid-open Patent Publication No. 2003-167684.